A report from Metro Vancouver, with contributions from Pacific Climate Impacts Consortium and Pinna Sustainability, warns that climate induced temperature changes in the Metro area are expected to rise 3 degrees Celsius by the 2050s, which will have a substantial impact on water resources, infrastructure, and management in the region.
Anticipated temperature and precipitation changes into the 2050s indicate that as the climate warms, the Metro Vancouver region can expect more than a doubling in the number of summer days above 25 Celsius, from an average of 22 days per year to 55 days per year.
The region’s annual precipitation is expected to increase by 5 per cent by the 2050s, and the periods of precipitation are expected to change. October and November should see the greatest increase in precipitation and the precipitation is expected to fall increasingly during extreme weather events.
- Approx. 30 per cent more precipitation is expected to fall on the 95th percentile wettest days;
- Approx. 60 per cent more on the 99th percentile wettest days;
- Precipitation volume of a 1-in-20 event could increase by 30 per cent;
- Conversely, summer rainfall is expected to decrease by 20 per cent, lengthening dry-spell duration by the same amount.
These events will have a strong impact on stormwater infrastructure and the region’s capacity to mitigate the negative consequences of overloaded stormwater systems. Overland flooding, combined sewer overflow and discharge, and diminished wastewater treatment can all be expected without changes to current infrastructure. Further, while the report did not directly calculate the anticipated growth of 1-in-50 and 1-in-100 year precipitation events, it’s expected that those events will see “even larger relative changes” than the increase in 1-in-20 year events.
The report strongly notes that the impacts on stormwater, public infrastructure, and human health necessitate further study to inform future design criteria for the necessary sectors.
Climate change in the Metro Vancouver area will also impact drinking water. Most of the region’s drinking water comes from mountain reservoirs fed by rainfall and snowmelt, the report noted. As was reported this week by the U.S.’s National Center for Atmospheric Research (NCAR), earlier snowmelt will translate into decreased streamflow in mountainous watersheds, which has been supported by recent computer modelling.
As both the NCAR and Metro Vancouver report, winter snowpack will be much less robust, affecting spring and summer streamflow and the available water resources. The Metro Vancouver report further notes that the increase in extreme rainfall events could cause greater turbidity in drinking water reservoirs.